Add ClickHouse output plugin

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

plugins/outputs/clickhouse/sample.conf

@@ -0,0 +1,24 @@
+# Save metrics to an SQL Database
+[[outputs.sql]]
+  ## Data source name
+  # data_source_name = ""
+
+  ## Timestamp column name
+  # timestamp_column = "timestamp"
+
+  ## Initialization SQL
+  # init_sql = ""
+
+  ## Maximum amount of time a connection may be idle. "0s" means connections are
+  ## never closed due to idle time.
+  # connection_max_idle_time = "0s"
+
+  ## Maximum amount of time a connection may be reused. "0s" means connections
+  ## are never closed due to age.
+  # connection_max_lifetime = "0s"
+
+  ## Maximum number of connections in the idle connection pool. 0 means unlimited.
+  # connection_max_idle = 2
+
+  ## Maximum number of open connections to the database. 0 means unlimited.
+  # connection_max_open = 0